Thermal Transient Performance of PEM Fuel Cells in Aerospace Applications: A Numerical Study.

Polymer electrolyte membrane fuel cells (PEMFCs) are gaining attention as viable energy carriers for future aerospace propulsion systems due to their high-power density, lightweight and compact design, zero emissions, scalability, quiet operation, and relatively reliable performance. However, maintaining optimal performance and durability under transient thermal conditions remains a critical challenge, particularly in aerospace environments. Despite extensive research on PEMFCs, the transient thermal effects remain underexplored. This study employs a validated numerical simulation model to investigate the transient responses of a PEMFC subjected to thermal shock cycles, where the bipolar plate walls experience abrupt temperature drops to 10 °C for durations of 3 to 19 s. The simulation model was benchmarked against experimental data from the literature, demonstrating deviations of less than 10% in the polarization curves, confirming its reliability for predicting transient behaviors. Results reveal that during these thermal shocks, the current density decreases by approximately 15%, from 9263 A/m at 50 °C to 7709 A/m at 10 °C, with recovery times exceeding 4 s. Significant deviations were observed in oxygen concentration, particularly at the cathode catalyst layer, where minimum levels decreased by over 20%. Similarly, the water content in the membrane showed an overshoot above steady-state levels postrecovery, remaining elevated for extended periods. Liquid water saturation in the gas diffusion layers (GDLs) increased significantly near the hydrogen inlets during cold conditions, obstructing reactant flow and further impacting performance. This study provides detailed predictions of the steady-state and transient responses of PEMFCs to temperature reduction cycles. The findings contribute to advancing thermal management strategies and improving system resilience under transient conditions, thereby addressing a key challenge in sustainable aviation.